Engine Running Rich Due to Fuel Leak Inside Intake Manifold on Oldsmobile Bravada

Vehicles using the enhanced vortec V6 engine may be hard to start run poorly and/or use to much fuel due to a fuel leak inside the intake manifold plenum. Commonly this is caused by a leaking fuel pressure regulator or fuel line. The fuel system will need to be pressurized with the upper intake manifold removed in order to determine the exact cause of the leak. Removing the "tuning valve" from the upper intake can allow for limited visual inspection without removing the upper intake manifold.

Average mileage: 150,000 (150,000–150,000)
3 model years affected: 1992, 1993, 1994
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problem details
1992 Oldsmobile Bravada 150,000 mi,
Engine running very rich, about 7 miles to the gallon is all I get, carbon builds up, exhaust is very rich in fuel smell. Have tried different things so far nothing works, could it be a sensor, have replaced different ones, still nothing works.